This paper examined the effect of organizational structure on employee performance in the Nigeria Social Insurance Trust Fund (NSITF) in Abuja, Nigeria. The structure of an organization is very vital in determining workers’ level of effectiveness and efficiency in achieving set goals and objectives which has a significant effect on organizational performance. The study utilized a survey research design. A population of 5100 employees of NSITF was used for the study. The sample size was made up of 481 respondents selected based on random and convenient sampling techniques. A well-structured questionnaire was used as an instrument to obtain relevant data for the survey. Out of the 481 questionnaires distributed, a total of 418 were retrieved. The method of data analysis was multiple regression analysis which was carried out with the aid of the Statistical Package for Social Sciences (SPSS) software version 27. The findings showed that organizational structure has a significant effect on employee performance. Findings showed that organizational structure (centralization, formalization, complexity, and specialization) had a positive and significant effect on employee performance (employee effectiveness) in NSITF Abuja, Nigeria. Organizational structure (centralization (CEN = 0.03 + 0.19), formalization (FOM = 0.03 + 1.22), complexity (COM = 0.03 + 1.17) and specialization (SPE = 0.03 + 1.14) was found to be positively significant. Therefore, the study recommends that for NSITF to continue to achieve high employee performance levels, it must ensure that the appropriate organizational structure is being implemented at the right time and under the right circumstances to promote employee satisfaction, innovation, effectiveness, and efficiency.